In belt drives with alternating driven and driving wheels and an according change from slack side to tight side the tightening of the slack side requires a tensioning device with two belt pulleys, which pre-stress the belt upstream and downstream in reference to the alternating driving and driven drive wheel. This typically but not mandatorily relates to a belt drive of an internal combustion engine with an electric engine in the form of a starter generator, which is not only driven by the internal combustion engine for the purpose of generating electricity but also drives the internal combustion engine in order to start it.
Tensioning devices of prior art, for example suggested in DE 199 26 615 A1, DE 10 2008 025 552 A1, and DE 10 2006 019 877 A1 each comprise a tensioning housing fastened at the starter generator and two tensioning arms supported therein in a mobile fashion, with their belt pulleys being impinged with a force in reference to each other by a spring means arranged between them in order to tighten the belt.
The tensioning device of the type mentioned at the outset, i.e. comprising only one tensioning arm supported mobile in the tensioning housing, on the one side, and a belt pulley fixed to the housing, on the other side, and an electric engine with such a tensioning device is known from the two papers DE 10 2011 082 764 A1 and DE 10 2011 082 330 A1 not preliminarily published. The friction of the friction bearing, considerably higher in reference to a roller bearing, allows in a simple fashion an adjustment of the friction moment, required for damping the oscillation of the tensioning housing swaying back and forth during operation, to a suitable level.